## Fixes
- [#3] Status events now add/update a status ActivityNode in timeline (upsertWsStatusNode)
- [#4] Done callback adds done node; error callback adds error node + sets session.status="error"
- [#5] handleRegenerate fully synced with workspace: status/tool/card/done/error all handled
- [#1][#2] localStorage persistence: completed/error sessions auto-saved, lazy-loaded on demand
- [#1] handleSelectConversation preloads workspace sessions from localStorage for history messages
- Refactored completeWsSession to include done ActivityNode in timeline
- Added errorWsSession, upsertWsStatusNode, saveWsToStorage, loadWsFromStorage helpers
## Known limitation
- [#7] workspace_card merge:true not yet used by backend (all cards are append-only for now)
- History workspace recovery depends on localStorage (browser-local, not cross-device)
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
